Diffusion-layer-free air cathode based on ionic conductive hydrogel for microbial fuel cells

High hydraulic pressure in air-cathode microbial fuel cells (MFCs) can lead to severe cathodic water leakage and power reduction, thereby hindering the practical applications of MFCs. In this study, an alternative air cathode without a diffusion layer was developed using a cross-linked hydrogel, oxidized konjac glucomannan/2-hydroxypropytrimethyl ammonium chloride chitosan (OM), for ion bridging. The cathode was placed horizontally to avoid hydraulic pressure on its surface. Ion transportation was sustained with a minimal OKH hydrogel loading of 10 mg/cm(2). A maximum power density of 1.0 +/- 0.04 W/m(2) was achieved, which was only slightly lower than the 1.28 +/- 0.02 W/m(2) of common air cathodes. Moreover, the cost of the OKH hydrogel is only $0.12/m(2), which can reduce similar to 85% of the cathode cost without using the advanced polyvinylidene fluoride diffusion layer. Therefore, the development of this new diffusion-layer-free air cathode using conductive ionic hydrogel provides a low-cost strategy for stable MFC operation, thereby demonstrating great potential for practical applications of MFC technology. (C) 2020 Published by Elsevier B.V.